Larger samples better than larger databases in autosomal genetics

June 2008 PLOS Genetics is out and the article that caught my attention this time is: Calibrating the Performance of SNP Arrays for Whole-Genome Association Studies by Ke Hao et al.

... according to our results a study employing N = 300 subjects and the Affy500K platform offers higher power than a study employs N = 250 subjects and the Ilmn650K platform. This 20% increase in sample size (N = 300 vs. N = 250) provides more power than the 90% increase in the number of SNPs genotyped (286K SNPs vs. 545K SNPs). In scenarios where funding becomes the constraining factor, our results suggest that genotyping larger sample size with cheaper SNP arrays might achieve better statistical power. On the other hand, if the constraining factor is the number of subjects, then it appears that SNP arrays offering the largest genetic coverage should be employed.